package com.some;

import java.util.Scanner;

public class Boss01_4 {
    public static int maxValue(int[] prices) {
        int n = prices.length;
        int buy1 = -prices[0], sell1 = 0;
        int buy2 = -prices[0], sell2 = 0;
        for (int i = 1; i < n; ++i) {
            buy1 = Math.max(buy1, -prices[i]);
            sell1 = Math.max(sell1, buy1 + prices[i]);
            buy2 = Math.max(buy2, sell1 - prices[i]);
            sell2 = Math.max(sell2, buy2 + prices[i]);
        }
        return sell2;
    }

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] prices = new int[n];
        for (int i = 0; i < n; i++) {
            prices[i] = sc.nextInt();
        }
        System.out.println(maxValue(prices));
    }
}
